1. Field of the Invention
The present invention relates to a coordinate input device wherein an operation area is operated by means of an input member such as an input pen to effect an input of data.
2. Description of the Related Art
A conventional coordinate input device will be described below with reference to FIGS. 9 to 13 all concerned with a conventional coordinate input device, of which FIG. 9 is a plan view of the device, FIG. 10 is a sectional view taken on line 10--10 in FIG. 9, FIG. 11 is a sectional view taken on line 11--11 in FIG. 9, FIG. 12 is a plan view of a lower substrate, and FIG. 13 is a rear view of a film substrate.
In the conventional coordinate input device, a lower substrate 21 formed of a transparent glass is provided with a rectangular body portion 21a and a terminal portion 21b formed in part of the body portion 21a.
On the whole of one side (upper surface) of the lower substrate 21 is formed a first transparent resistance film 22 using indium oxide.
On the transparent resistance film 22 are formed a pair of first electrode portions 23a and 23b formed of silver for example and which are parallel to each other. Between the electrode portions 23a and 23b there is formed an operation area 24 in the direction of X axis.
As shown in FIG. 12, on the transparent resistance film 22 on the lower substrate 21 there are formed a pair of first lead-out electrodes 25a and 25b formed of silver for example and drawn out from the electrode portions 23a and 23b to the terminal portion 21b while keeping out of the operation area 24 and a pair of second lead-out electrode portions 26a and 26b formed of silver for example and extending from the terminal portion 21b to the body portion 21a in the vicinity of the terminal portion 21b, the lead-out electrode portions 26a and 26b being formed spacedly from and alternately with the lead-out electrode portions 25a nd 25b.
In an exposed state of the electrode portions 23a, 23b and the operation area 24, a first insulating film 27 is formed on the transparent resistance film 22 and also on the first and second lead-out electrode portions 25a, 25b, 26a, 26b, the insulating film 27 being cut out at end portions of the second lead-out electrode portions 26a and 26b to give exposed portions 28a and 28b.
As shown in FIGS. 10, 11 and 13, a second transparent resistance film 30 is formed using indium oxide on the whole of one side (lower surface) of an upper film substrate 29, the upper film substrate 29 being formed of a transparent synthetic resin, and a pair of second electrode portions 31a and 31b formed of silver for example and parallel to each other are formed on the transparent resistance film 30 on the film substrate 29, with an operation area 32 being formed in the direction of Y axis between the electrode portions 31a and 31b.
On the transparent resistance film 30 are formed a pair of third lead-out electrode portions 33a and 33b formed of silver for example, the electrode portions 33a and 33b being drawn out in L shape from the electrode portions 31a and 31b while keeping out of the operation area 32
With the electrode portions 31a, 31b and the operation area 32 exposed, a second insulating film 34 is formed on the transparent resistance film 30 and also on the third lead-out electrode portions 33a, 33b, the insulating film 34 being cut out at end portions of the third lead-out electrode portions 33a and 33b to give exposed portions 35a and 35b. When the film substrate 29 is superimposed on the lower substrate 21, the exposed portions 35a and 35b become opposed to the exposed portions 28a and 28b.
As shown in FIG.11, an electrically conductive adhesive 36 which comprises a thermosetting or thermoplastic resin with electrically conductive particles such as silver particles is applied between the exposed portions 28a, 28b and the exposed portions 35a, 35b. With the electrically conductive adhesive 36, the electrode portions 31a and 31b are drawn out electrically to the second lead-out electrode portions 26a and 26b.
As shown in FIGS. 10 and 11, dot spacers 37 are disposed between the first and second transparent resistance films 22, 30.
The electrically conductive adhesive 36 is applied to the second exposed portions 28a and 28b of the lower substrate 21. If the film substrate 29 is superimposed on the lower substrate 21 through the dot spacers 37, allowing the exposed portions 35a and 35b to come into opposition to the exposed portions 28a and 28b and if in this state heat and pressure are applied, the thermosetting resin will cure to bond the second lead-out electrode portions 26a, 26b and the third lead-out electrode portions 33a, 33b with each other and in this bonded state the second and third lead-out electrode portions will be electrically connected together through electrically conductive particles.
As shown in FIG. 9, a flat cable 38, which is formed of a flexible synthetic resin, comprises a base portion 38a, a mounting portion 38b provided at an end of the base portion 38a, and a plurality of conductor portions 39 extending through both base portion 38a and mounting portion 38b.
The flat cable 38 is disposed so that its conductor portions 39 are opposed to the first and second lead-out electrode portions 25a, 25b, 26a, 26b of the lower substrate 21 and are connected thereto using an electrically conductive adhesive (not shown).
The connection between the conductor portions 39 and the first and second lead-out electrode portions 25a, 25b, 26a, 26b is conducted by applying an electrically conductive adhesive onto those lead-out electrode portions, placing the conductor portions 39 thereon and applying heat and pressure.
Inputted data are extracted electrically from the coordinate input device through the flat cable 38.
In operation, the film substrate 29 is pushed with an input member on its side opposite to the operation area 32, thereby causing the film substrate 29 and the second transparent resistance film 30 to be deformed and allowing the transparent resistance film 30 to come into contact with the transparent resistance film 22, whereby desired characters and patterns can be inputted. The data thus inputted are extracted from the first and second lead-out electrode portions 25a, 25b and 26a, 26b and are extracted to the exterior through the flat cable 38.
In the conventional coordinate input device, the first and second lead-out electrode portions 25a, 25b, 26a, 26b provided on the lower substrate 21 and the conductor portions 39 of the flat cable 38 are connected together using an electrically conductive adhesive and so are between the third lead-out electrode portions 33a, 33b formed on the film substrate 29 and the second lead-out electrode portions 26a, 26b formed on the lower substrate 21 using the electrically conductive adhesive 36. These connecting operations are troublesome, leading to low productivity and high cost.
Further, since the first and second lead-out electrode portions 25a, 25b and 26a, 26b are arranged in an alternate manner, the electrically conductive adhesive 36 cannot follow up a great difference in the amount of elongation caused by thermal expansion between the lower substrate 21 formed of glass and the film substrate 29 formed of a synthetic resin, thus giving rise to the problem that the electrically conductive adhesive 36 comes off and there occurs a defective connection